10 research outputs found
High-Dimensional Pixel Entanglement: Efficient Generation and Certification
Photons offer the potential to carry large amounts of information in their
spectral, spatial, and polarisation degrees of freedom. While state-of-the-art
classical communication systems routinely aim to maximize this
information-carrying capacity via wavelength and spatial-mode division
multiplexing, quantum systems based on multi-mode entanglement usually suffer
from low state quality, long measurement times, and limited encoding capacity.
At the same time, entanglement certification methods often rely on assumptions
that compromise security. Here we show the certification of photonic
high-dimensional entanglement in the transverse position-momentum
degree-of-freedom with a record quality, measurement speed, and entanglement
dimensionality, without making any assumptions about the state or channels.
Using a tailored macro-pixel basis, precise spatial-mode measurements, and a
modified entanglement witness, we demonstrate state fidelities of up to 94.4%
in a 19-dimensional state-space, entanglement in up to 55 local dimensions, and
an entanglement-of-formation of up to 4 ebits. Furthermore, our measurement
times show an improvement of more than two orders of magnitude over previous
state-of-the-art demonstrations. Our results pave the way for noise-robust
quantum networks that saturate the information-carrying capacity of single
photons
Entangled ripples and twists of light:Radial and azimuthal Laguerre-Gaussian mode entanglement
It is well known that photons can carry a spatial structure akin to a
"twisted" or "rippled" wavefront. Such structured light fields have sparked
significant interest in both classical and quantum physics, with applications
ranging from dense communications to light-matter interaction. Harnessing the
full advantage of transverse spatial photonic encoding using the
Laguerre-Gaussian (LG) basis in the quantum domain requires control over both
the azimuthal (twisted) and radial (rippled) components of photons. However,
precise measurement of the radial photonic degree-of-freedom has proven to be
experimentally challenging primarily due to its transverse amplitude structure.
Here we demonstrate the generation and certification of full-field
Laguerre-Gaussian entanglement between photons pairs generated by spontaneous
parametric down conversion in the telecom regime. By precisely tuning the
optical system parameters for state generation and collection, and adopting
recently developed techniques for precise spatial mode measurement, we are able
to certify fidelities up to 85\% and entanglement dimensionalities up to 26 in
a 43-dimensional radial and azimuthal LG mode space. Furthermore, we study
two-photon quantum correlations between 9 LG mode groups, demonstrating a
correlation structure related to mode group order and inter-modal cross-talk.
In addition, we show how the noise-robustness of high-dimensional entanglement
certification can be significantly increased by using measurements in multiple
LG mutually unbiased bases. Our work demonstrates the potential offered by the
full spatial structure of the two-photon field for enhancing technologies for
quantum information processing and communication
Characterizing and Tailoring Spatial Correlations in Multimode Parametric Down-Conversion
Photons entangled in their position-momentum degrees of freedom (DoFs) serve
as an elegant manifestation of the Einstein-Podolsky-Rosen paradox, while also
enhancing quantum technologies for communication, imaging, and computation. The
multi-mode nature of photons generated in parametric downconversion has
inspired a new generation of experiments on high-dimensional entanglement,
ranging from complete quantum state teleportation to exotic multi-partite
entanglement. However, precise characterisation of the underlying
position-momentum state is notoriously difficult due to limitations in detector
technology, resulting in a slow and inaccurate reconstruction riddled with
noise. Furthermore, theoretical models for the generated two-photon state often
forgo the importance of the measurement system, resulting in a discrepancy
between theory and experiment. Here we formalise a description of the
two-photon wavefunction in the spatial domain, referred to as the collected
joint-transverse-momentum-amplitude (JTMA), which incorporates both the
generation and measurement system involved. We go on to propose and demonstrate
a practical and efficient method to accurately reconstruct the collected JTMA
using a simple phase-step scan known as the -measurement. Finally, we
discuss how precise knowledge of the collected JTMA enables us to generate
tailored high-dimensional entangled states that maximise discrete-variable
entanglement measures such as entanglement-of-formation or entanglement
dimensionality, and optimise critical experimental parameters such as photon
heralding efficiency. By accurately and efficiently characterising photonic
position-momentum entanglement, our results unlock its full potential for
discrete-variable quantum information science and lay the groundwork for future
quantum technologies based on multi-mode entanglement.Comment: 19 pages, 9 figure
Genuine High-Dimensional Quantum Steering
High-dimensional quantum entanglement can give rise to stronger forms of
nonlocal correlations compared to qubit systems. Beyond being of fundamental
interest, this offers significant advantages for quantum information
processing. The problem of certifying these stronger correlations, however,
remains an important challenge, in particular in an experimental setting. Here
we theoretically formalise and experimentally demonstrate a notion of genuine
high-dimensional quantum nonlocal steering. We show that high-dimensional
entanglement combined with judiciously chosen local measurements can lead to a
stronger form of steering, provably impossible to obtain via entanglement in
lower dimensions. Exploiting the connection between steering and
incompatibility of quantum measurements, we derive simple two-setting steering
inequalities for certifying the presence of genuine high-dimensional steering.
We report the experimental violation of these inequalities using macro-pixel
photon-pair entanglement certifying genuine high-dimensional steering in
dimensions up to . Our work paves the way for the characterisation and
certification of quantum nonlocal correlations in high-dimensional systems.Comment: 9 pages, 1 table, 5 figure
Noise-Robust and Loss-Tolerant Quantum Steering with Qudits
A primary requirement for a robust and unconditionally secure quantum network
is the establishment of quantum nonlocal correlations over a realistic channel.
While loophole-free tests of Bell nonlocality allow for entanglement
certification in such a device-independent setting, they are extremely
sensitive to loss and noise, which naturally arise in any practical
communication scenario. Quantum steering relaxes the strict technological
constraints of Bell nonlocality by re-framing it in an asymmetric manner, thus
providing the basis for one-sided device-independent quantum networks that can
operate under realistic conditions. Here we introduce a noise-robust and
loss-tolerant test of quantum steering designed for single detector
measurements that harnesses the advantages of high-dimensional entanglement. We
showcase the improvements over qubit-based systems by experimentally
demonstrating detection loophole-free quantum steering in 53 dimensions through
simultaneous loss and noise conditions corresponding to 14.2 dB loss equivalent
to 79 km of telecommunication fibre, and 36% of white noise. We go on to show
how the use of high dimensions counter-intuitively leads to a dramatic
reduction in total measurement time, enabling a quantum steering violation
almost two orders of magnitude faster obtained by simply doubling the Hilbert
space dimension. By surpassing the constraints imposed upon the
device-independent distribution of entanglement, our loss-tolerant,
noise-robust, and resource-efficient demonstration of quantum steering proves
itself a critical ingredient for making device-independent quantum
communication over long distances a reality.Comment: 12 pages, 1 table, 7 figure
Unveiling the Non-Abelian Statistics of <i>D</i>(<i>S</i><sub>3</sub>) Anyons Using a Classical Photonic Simulator
Simulators can realize novel phenomena by separating them from the complexities of a full physical implementation. Here, we put forward a scheme that can simulate the exotic statistics of D(S3) non-Abelian anyons with minimal resources. The qudit lattice representation of this planar code supports local encoding of D(S3) anyons. As a proof-of-principle demonstration, we employ a classical photonic simulator to encode a single qutrit and manipulate it to perform the fusion and braiding properties of non-Abelian D(S3) anyons. The photonic technology allows us to perform the required nonunitary operations with much higher fidelity than what can be achieved with current quantum computers. Our approach can be directly generalized to larger systems or to different anyonic models, thus enabling advances in the exploration of quantum error correction and fundamental physics alike.</p